This invention relates generally to an air flow deflector device that is principally operative to reduce air stream flowinduced excessive pressure oscillations occurring in the open cavities of aircraft, aerospace and other vehicles operating particularly at relatively high speeds.
An important problem involved in the accurate aerial delivery of weapons and other stores on selected targets concerns the excessive pressure oscillations caused or induced by the flow of the air stream past the cavity or cavities containing such weapons or other stores. When these cavities have been opened in preparation for the release of such stores, the relatively high speed air stream flow past the so-called "shield" area, which is the area of flow immediately over or under the opened cavity, will cause relatively large pressure oscillations at the said shield area and thus within the cavity itself. This phenomenon, which is also known as cavity resonance, can and has caused damage or even destruction of the vehicle structure or stores contained in the open cavity, and, moreover, may also result in damage to or malfunction of equipment and even adversely affect the operation of the vehicle itself. The obvious disadvantage of the latter, for example, to a bomber aircraft on a bombing run is self-evident. Finally, such excessive pressure oscillations, particularly when coupled with turbulent flow immediately outside of the cavity, can easily cause the released bombs or other stores to tumble further affecting their accurate release on target.
Previous efforts have been made for many years to solve, or, at least, to reduce the aforementioned instability effects of the excessive pressure oscillations and/or turbulence resulting from the air flow past the open cavity and even the entry thereof into the cavities itself. In one example, taught in U.S. Pat. No. 2,451,479, issued to W. S. Diehl on Oct. 19, 1948, there is illustrated a flow controlling screen that is disposed in the path of the free stream flow past an open bomb bay at the leading edge thereof. Naturally, with the use of such a screen, the turbulence of the free stream flow obviously tends to be reduced. However, although this arrangement appeared to offer some advantage in reducing the overall circulation of the free stream air in the open bomb bay compartment due to the diffusion effect on the air stream, its use in reducing buffeting therein appears to be minimal. More importantly, the use of such a screen suffers from the significant disadvantage of offering, in addition, very high aerodynamic resistance, particularly when considered in the light of the much faster cruising speeds of today's bomber and other aircraft and aerospace vehicles. Finally, its effect on reducing cavity resonance appears minimal.
A second principal solution offered to alleviate the foregoing problem of the excessive turbulence produced in the open cavities of aerospace and other vehicles due to the free stream flow thereinto and also, perhaps, reduce the aforementioned cavity resonance involves the use of some kind of a flap or vane deflector. In this regard, in another U.S. Pat. No. 2,243,906, issued to A. Huet on June 3, 1941, it was proposed to use one or more flaps disposed in front of the forward vehicle, representing for example, the lead car or two or more interconnected cars naturally constituting a train. The aforementioned flaps or vanes are installed forwardly of the forward car, for example, of the train, as noted hereinbefore, for the purpose of creating a so-called "stream-lined" air flow around the car, without the body of the car itself being required to be stream-lined. Thus, the inherent resistance to the air, or, in other words, the drag of the car is reduced in this way in accordance with the teachings of the aforementioned U.S. Pat. No. 2,243,906 system. A further reduction in the resistance offered by the surrounding air is also taught by the latter patent by adding other flap deflectors at the gaps between the interconnected cars for eliminating eddy currents normally formed thereat.
In still another patent; namely, U.S. Pat. No. 2,749,064, issued to W. H. Kuhlman on June 5, 1956, a flap element is pivoted to the fuselage of a bomber aircraft just ahead of the bomb bay thereof. It is stated in this patent that plain flaps mounted forwardly of the bomb bay for directing the air stream over the open bomb bay are already known. However, such plain flaps, though certainly offering some improvement in generally reducing air turbulence and thus a decreased air flow into the bomb bay to thereby reduce the buffeting effect thereof, they have practically no effect on the pitching moment being imparted to the bomb or other store after its release from the bomb bay. As a further improvement, the aforementioned Kuhlman patent provides a flap or deflector surface that is combined with a grid. The flap is pivoted to the aircraft fuselage just forwardly of the bomb bay for a selective adjustment between a flush relation and an extended relation in the air stream to a positive angle of attack. This flap is improved over the so-called "plain" flap of previous proposals by being so pivoted that, when it is in its extended position, the leading edge thereof is made specifically spaced from the bottom of the fuselage of the aircraft to provide what is, in effect, a slot or narrow passage between the flap and fuselage. In this manner, a portion of the air stream flows through the said passage and is diffused thereby and its velocity thus diminished to reduce the air turbulence that would, but for the spaced flow diverter flap, be otherwise created thereby. This turbulence is further reduced, as is disclosed in the aforementioned Kuhlman patent, by the combination of a grid member with the above-noted spaced flap, which grid extends from adjacent the trailing edge of the flap into the path of the air flow from and rearwardly of the slot or passage between the flap and aircraft to thereby provide for the further control and reduction of air turbulence. On the other hand, the unique flow deflector device and diffuser assembly of the present invention, to be set forth hereinafter in the following summary and detailed description, is considered to constitute a still further improvement in that it places a novel deflector flap device at the trailing edge of the cavity and, as such, is designed principally to reduce the previously-referred to phenomenon of cavity resonance, whereas the aforementioned previously-noted proposals, using flaps at the forward edge of the cavity, as in the Kuhlman patent, are directed primarily to the reduction in the turbulence of the air flow.